6100 MPS-B Programming Manual

INTRODUCTION TO 6100 MPS-B
Features of the 6100 MPS-B Product
FEATURES OF THE 6100 MPS-B PRODUCT
The 6100 MPS-B protocol module runs in a Line Interface Unit
(LIU) on a 6100 communication subsystem. It is downloaded from a
disk file to the LIU, either when the system is cold-loaded or by
operator request. A single copy of 6100 MPS-B controls one data
communication line.
Applications use the line by making file system requests. Some
calls, such as OPEN, CLOSE, SETMODE, and so forth, are handled by
the I/O process; others contain tasks for the protocol module. A
protocol module task request is encoded in a WRITEREAD call; the
"write" part of the call delivers the request to the LIU, and the
"read" part carries the response message back to the application.
Table 1-1 lists the requests an application can make to 6100
MPS-B.
NOTE
Table 1-1 does not show requests that are issued only by
Tandem-supplied software. Because these requests may still
be reflected on the output from a trace, Section 3 includes
a list of their function codes.
Notice that some requests have the same names as GUARDIAN file
system calls. For example, the 6100 MPS-B READ request is
different from the GUARDIAN READ call. Also, 6100 MPS-B START
LINE and STOP LINE requests are not the same as the CMI commands
START and STOP with LINE as the object to be acted upon. To
avoid ambiguity, this book uses call, command, or request to
qualify such names. (Thus, a READ call is a GUARDIAN call--
which has some request encoded in it--while a READ request is a
specific function for the protocol module. Further, a START LINE
command is a directive for CMI, while a START LINE request is
directed to the protocol module).
Also notice that some requests perform a variety of functions.
In some cases, you specify the function you want performed. In
other cases, the function to be performed is implied by the
request. Section 3 of this book describes the requests in
detail.
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